Non-invasive blood pressure (NiBP) monitoring is a non-invasive means of assessing a patient's circulatory and cardiovascular status. The ejection of blood from the left side of the heart initiates a pressure wave that precedes the actual flow of blood. The wave of pulsating blood causes turbulence and vibrations of the blood vessel walls. With an inflatable cuff applied to patient's limb (arm or leg), an NiBP monitor measures a patient's arterial blood pressure by detecting these arterial wall vibrations, which are known as Korotkoff signals.
An automatic NiBP monitoring system comprises a cuff, air pump, valves, pressure sensors, and hoses, typically contained in an enclosure. The air pump compresses the air and inflates the cuff. Valves control the inflation and deflation of the cuff. Control electronics control the operation of the pump and valves, receive signals from the pressure sensors, and calculate the blood pressure from these signals.
Traditionally an automatic NiBP monitoring system takes the air used for inflating the cuff in through the enclosure which has a port to the ambient air. When the cuff is deflated, the air from the cuff is also vented through the enclosure to the port to the ambient air. This means that moisture and/or contaminants in the ambient air pass through the enclosure when the cuff is inflated, and then again when the cuff is deflated.
It is often desirable to monitor a patient's blood pressure while a patient is ambulatory. For such cases, a handheld or wearable NiBP monitoring system might be used. Electronics, such as the control electronics in an automatic NiBP monitoring system, are sensitive to the presence of water and/or other such contaminants, and may malfunction in their presence. A water proof or water resistant NiBP monitoring system is needed so that the patient may be monitored and still be able to perform normal functions such as showering, bathing, washing, etc. In such a system, it is also desirable that the air channel be cleanable so that contaminants which accumulate in the air channel may be removed to maintain the proper operation of the system.